The objective of the present proposal is to provide new insights into the functions of the basal ganglia through application of the comparative approach. The functions of the basal ganglia have been a matter of long standing scientific interest due to the fact that diseases of the basal ganglia in humans such as Parkinsonism, Huntington's chorea, athetosis and hemiballismus constitute major health problems. In mammals the basal ganglia appear to integrate sensory and motor information received from widespread regions of the neocortex. The major efferent projections of this system, however, are also directed back to these same regions of the telencephalon. For this reason it has proven difficult to determine the specific information processing functions of the basal ganglia. This question can be approached more directly in avian and reptilian species in which the telencephalon is not laminated in the manner of mammalian neocortex. For example, in pigeons the sole population of telencephalic neurons projecting upon the basal ganglia is contained in a restricted cell field of the lateral telencephalic wall. A different portion of the telencephalon in this species then receives projections in return from the basal ganglionic circuit. Specific experiments proposed include a detailed study of the neurotransmitters and anatomical connections of neurons in the basal ganglionic systems of pigeons and Caiman crocodilus. A study of changes in metabolic activity of cells in the basal ganglionic systems of these species resulting from the performance of spatial orientation tasks is also proposed.